Driving balance-wheel for an electrical timepiece



A. HUG ETAL 3,161,012

DRIVING BALANCE-WHEEL FOR AN ELECTRICAL. TIMEPIECE Dec. 15, 1964 Filed Aug. 1, 1963 Ill Q 'III/IIIIIIIIII) 1 United States Patent 3,161,tll2 DRIVTNG BALANCE-WHEEL FOP. AN ELECTRTtiAL TEMEPIECE Andre Hog and Rene Meister, Nenchatel, Switzerland, as-

signors to Ehanclres S.A., Neuchatel, Switzerland, :1 iirrn of Switzerland Filed Aug. 1, 1963, Ser. No. 299,287 Claims priority, application Switzerland, Aug. 22, 1962, 9,990/62 2 Claims. (Cl. 58--28) The present invention pertains to a driving balancewheel for an electrical timepiece.

The driving balance-Wheels for electrical time-pieces, which comprise a magnetic circuit often provided with two permanent magnets and with elements made of magnetic material, are difficult to be manufactured, due the hardness of the magnetic material, which can be ditlicnlt to work, and due to the relatively high weight of the magnets.

An object of the present invention is to provide such a balance-wheel which is constituted and arranged in such a Way that its construction is simple and easy.

A balance-wheel according to the invention is characterized by the fact that it comprises two parallel circular plates, made of a non-magnetic material. Each of the plates carries two permanent magnets connected by an armature made of magnetic material, having the shape of a segment of crown, located in an opening of corresponding shape provided in each of the plates. Each magnet of one plate is located in the neighborhood of one of the extremities of one of the armatures, opposite one of the magnets of the other plate. Accordingly the ".edian plane of the magnetic field so created has the shape of a loop directed par allelly to the axis of the balance-wheel and perpendicularly to the diametral plane of symmetry of the latter.

Other objects, features and advantages of the invention will be apparent from the following detailed description when read with the drawings which show, by way of example, one embodiment of the invention. In the drawings:

FIG. 1 is a plan View of a part of a balance-wheel of a timepiece, and

FIG. 2 is an axial section, along line 11-11 of FIG. 1.

The balance-Wheel represented in FIGS. 1 and 2 comprises a shaft 1 on which is mounted a sleeve 2 constituting a brace between two parallel circular plates 3 and 4, made of non-magnetic material. In each of these two plates there is milled a recess 5, having the shape of an arc of a circle, located in the neighbourhood of their periphery. Fixed into recess 5 is a small plate 6, made of magnetic material, having the shape of a segment of crown. The two small plates 6 of the circular plates 3 and 4 are located opposite one another.

Each circular plate 3 and 4 is provided with two holes provided in its part constituting the bottom of the recess 5. A permanent magnet 7, is forced in each of these holes, its rear axial face being in contact with one of the small plates 6.

Each magnet '7 of one of the circular plates 3 and 4 is situated opposite one of the magnets of the other plate. There is thus formed a magnetic circuit having the shape of a loop, the median plane of which, schematically represented by the line 8 in FIG. 1, is parallel to the axis 1 of the balance-wheel and is perpendicular to the diametral plane of symmetry 9 of the balance-wheel.

Each of two plates 3 and i carry moreover a counterweight lti having the shape of a segment of crown, serving to balance the weight of the magnet '7 and ot the armature 6. These counterweights are forced into recesses 11 provided in the circular plates 3 and 4. The fine balancing of the balance-Wheel is obtained by boring radial holes 12 in the connterweights 1%.

What we claim is:

l. A driving balance-wheel for an electrical timepiece comprising two parallel circular plates of non-magnetic material, a shaft for supporting said plates for rotational motion, a recess having the shape of a segment of a circle in each of said plates adjacent the periphery thereof, an armature plate of magnetic material having the shape of a segment of a circle in each of said recesses, 11 pair of spaced permanent magnets fixed to each of said armatures, the magnets 01' one pair being disposed opposite the magnets of the other pair, said permanent magnets being polarized to establish a magnetic field in the form of a loop passing through said paths of permanent magnets and said armatures wherein the median plane of the magnetic field is parallel to the axis of said balance-wheel and perpendicular to the diametral plane of symmetry of said balance-wheel, and a counterweight in the shape of a segment of a circle fixed to each of said plates near the periphery thereof and diametrically opposite aid recesses.

2. The driving balance-wheel of claim 1, wherein each of said plates includes a second recess and said counterweight is fixed in said second recess.

References Cited by the Examiner UNITED STATES PATENTS 2,986,683 5/61 Lavet et al. 5828 3,056,253 10/62 Beyner et al. 58*28 FOREIGN PATENTS 209,269 5/60 Austria.

LEYLAND M. MARTIN, Primary Examiner.

JOSEPH P. STRIZAK, Examiner, 

1. A DRIVING BALANCE-WHEEL FOR AN ELECTRICAL TIMEPIECE COMPRISING TWO PARALLEL CIRCULAR PLATES OF NON-MAGNETIC MATERIAL, A SHAFT FOR SUPPORTING SAID PLATES FOR ROTATIONAL MOTION, A RECESS HAVING THE SHAPE OF A SEGMENT OF A CIRCLE IN EACH OF SAID PLATES ADJACENT THE PERIPHERY THEREOF, AN ARMATURE PLATE OF MAGNETIC MATERIAL HAVING THE SHAPE OF A SEGMENT OF A CIRCLE IN EACH OF SAID RECESSES, A PAIR OF SPACED PERMANENT MAGNETS FIXED TO EACH OF SAID ARMATURES, THE MAGNETS OF ONE PAIR BEING DISPOSED OPPOSITE THE MAGNETS OF THE OTHER PAIR, SAID PERMANENT MAGNETS BEING POLARIZED TO ESTABLISH A MAGNETIC FIELD IN THE FORM OF A LOOP PASSING THROUGH SAID PATHS OF PERMANENT MAGNETS AND SAID ARMATURES WHEREIN THE MEDIAN PLANE OF THE MAGNETIC FIELD IS PARALLEL TO THE AXIS OF SAID BALANCE-WHEEL AND PERPENDICULAR TO THE DIAMETRAL PLANE OF SYMMETRY OF SAID BALANCE-WHEEL, AND A COUNTERWEIGHT IN THE SHAPE OF A SEGMENT OF A CIRCLE FIXED TO EACH OF SAID PLATES NEAR THE PERIPHERY THEREOF AND DIAMETRICALLY OPPOSITE SAID RECESSES. 